Timepiece dials must have superior visual recognition characteristics as practical products, and a superior aesthetic appearance as decorative products. Conventionally, in order to achieve such objects, metal materials such as Au, Ag, and the like have generally been used as the constituent materials of timepiece dials.
On the other hand, in order to lower production costs, increase the degree of freedom of molding of the timepiece dial, and the like, there have been attempts to use plastics as a substrate, and to form coating films composed of metal materials on the surface of such a substrate (for example, see Patent Reference 1).
However, plastics are generally inferior in terms of adhesion to metal materials. Accordingly, peeling tends to occur between the substrate and the coating film, so that the problem of inferiority of the timepiece dial in terms of durability has been encountered.
Furthermore, for example, in the case of radio-controlled timepieces and solar timepieces (timepieces equipped with solar cells), the ability to transmit electromagnetic waves (radio waves, light) is required in the timepiece dial. Accordingly, although plastics have been used in such timepiece dials, the external appearance of plastics lacks refinement. Consequently, in order to improve the aesthetic appearance of such timepiece dials, attempts have been made to coat such timepiece dials with thin films composed of metal materials. However, as was described above, the following problem has been encountered; namely, plastics are inferior in terms of adhesion to metal materials. Furthermore, in order to increase the transmissivity with respect to electromagnetic waves (radio waves, light), it is necessary to make the film sufficiently thin. In this case, however, the following problem is encountered; namely, if the film is made sufficiently thin, the aesthetic appearance of the timepiece dial as a whole is adversely affected.
[Patent Reference 1] Japanese Patent Application Laid-Open No. 2003-239083 (page 4, left column, lines 37 through 42).